1. Technical Field
The present invention relates to an optical element, a method for manufacturing the same, and an electronic apparatus.
2. Related Art
For example, in a projector that is a type of electronic apparatus, optical elements are disposed at each side of a liquid light valve. The optical element may be a wire grid polarization element disclosed in JP-A-2012-98469. The polarization element includes a transparent substrate and a metal grid disposed over the substrate in such a manner that the ribs or bar members of the grip are arranged with a pitch smaller than the wavelength of light used.
Since this grid is made of an inorganic material, the polarization element is less likely to deteriorate than polarization elements using an organic material, even if it is irradiated with light, and is thus useful for brighter liquid crystal projectors which are increasingly in demand.
For example, in a process for manufacturing a polarization element, a multilayer composite is formed on a substrate by forming an aluminum layer, a silicon oxide layer, and a silicon layer in this order on a substrate, and a resist pattern is formed in a striped manner on the composite. The multilayer composite is then etched at one time using the resist pattern as a mask, and is thus formed into a multilayer grid in a striped manner with a large aspect ratio in plan view.
Unfortunately, the grid has a multilayer structure with a large aspect ratio and the layers forming the multilayer structure have different etching rates. Consequently, the amount of etching is varied. If etching is intended to be performed up to the interface between the lowermost aluminum layer and the substrate, therefore, the etching must be performed allowing for variation in etching amount. Consequently, the side surfaces of the stripes of the multilayer structure are excessively etched, and the width of the stripes is reduced. Thus, it is difficult to form a small and fine polarization element.